Gulf Of Mexico's First Application Of Riserless Mud Return For Top-hole Drilling—A Case Study

Abstract:

This paper describes the preparation and operation for the first use of a riserless mud recovery (RMR) system on the top-hole section of a well in the Gulf of Mexico.  The material includes pre-well engineering and preparations including hydraulic analysis, pre-job vessel inspection, construction of new equipment, installation, pre-well planning decisions, and rationale for decisions.  In addition also discussed are benefits including improved wellbore quality due to use of an engineered drilling fluid, logistics savings from reduction of drilling fluids, and minimized environmental impact.  The paper also includes descriptions of equipment installation and testing onboard the drilling vessel operations during drilling, problems encountered and lessons learned from the operation.  A description of all equipment is included in the paper along with specifications and operation parameters. 

An RMR system has application in the top-hole drilling of oil and gas wells.  Using conventional methods, drilling fluid pumped down the drillstring during operations flows out onto the sea floor; this is often referred to as “Pump and Dump”.  RMR collects the mud at the mud line and pumps the fluid back to the rig where it is reconditioned and reused.  It allows the use of engineered drilling fluids and has possible applications for all offshore drilling.

RMR was deployed on a dynamically positioned vessel, and successfully used to drill the 26-in. hole section.  Drilling fluid recovered from the mud line back to the drillship was processed and reused, resulting in significant reduction in the volume of mud required for this top-hole section.  RMR reduced costs through savings in drilling fluid and improved well construction.

RMR is applicable to the drilling of top-holes in the entire Gulf of Mexico.  It has significant potential to reduce top-hole drilling costs, eliminate casing stings, extend casing shoe depths, drill through and past problem formations and improve the wellbore by eliminating washouts and shallow hazards.